This invention relates to ship design in general. Particularly, this invention relates to a sectioned ship which comprises at least a fore and an aft ship bodies whereby these ship bodies are connected by horizontal hinge means that permits limited pivoting movement relative to each other in a vertical direction to form a ship vessel.
In each harbor or quay there are specific restrictions on ship""s draft and dimensions, depending upon factors such as the local terrain and water""s depth. On those vessels that are to avail themselves the passage of the Panama Canal, as a rule, more restrictive measures are imposed, due to the special limits of three sets of locks of the canal. The dimensions of a merchant vessel is obviously related to its shipping cost, in that, generally speaking, the larger the ship""s hold, the lower the cost, in terms of either unit weight or unit volume of the ship""s load. This is good enough a reason for building larger and larger merchantmen. Now, any respectable merchantman sailing between the east and west coasts of North America takes advantage of the Panama Canal, because, if otherwise, different routes like rounding Cape Horn or wriggling through the Magellan Straits would instantly bring to mind the senseless tedium of a voyage no shorter than 8,000 nautical miles, not to mention the heavily added cost and risk. Thus, such a vessel is for ever subject to the limits of the Panama Canal, or so it seems. Anyhow, to increase ship""s hold so as to reduce shipping cost makes large vessels desirable; but the dimensions of a merchant ship must meet the various requirements of the harbors and quays it is to stop by, or those of the canals it is bound to negotiate and pass.
There is another consideration pertinent to this disclosure. A ship sailing at high sea is constantly subject to pitching and rolling, and it is not uncommonly known that pitching affects the ship""s structural strength much more than rolling does, because this motion always leads to hogging and/or sagging more or less noticeable. Hogging refers to the longitudinal bending of a ship when its center section is raised while the bow and stern are lowered. This phenomenon arises often at sea when the length and angle of incidence of waves is such that a crest supports the center while bow and stem are over the troughs; or, though rarely nowadays, it may arise when cargo is badly distributed, with the heaviest weights at the extremes. As to sagging, this term refers to the longitudinal bending of a ship as the bow and stern are raised while the center is lowered. Sagging occurs oftener than hogging, and it can be a severe strain on the hull. The phenomenon arises at sea when the length and angle of incidence of waves is such that the crests support the ends of the ship while the center is in a trough, or when heavy cargo is concentrated in the center of the ship""s length. In short, hogging and sagging refer to deflection of the hull of a ship, and they can be explained in terms of bending moment, a matter of material mechanics. The term moment is defined as the product of a force and the distance between the force and where moment is to be calculated. At any transverse section of a beam, the algebraic sum of the moments of all the forces to either side of the section is called the bending moment at that location. Gravity and buoyancy are significant factors in the consideration of a ship""s stability. And the influence of gravity includes ship""s weight itself and ship""s load. The larger and especially the longer the ship is, the greater the longitudinal bending moment when the ship is being pitched, and, as a consequence, the greater danger of hogging and sagging. Accordingly, to prevent the enlarged vessel from being actually hogged or sagged at sea and going down with men and mice, the vessel""s structural strength must be enforced, and this means the use of thicker steel plate for the hull and stronger materials for other structural members, hence, in the course of nature, increases the vessel""s weight, and usually a greater engine or power generator becomes a must.
To evaluate the longitudinal bending moment distribution along a ship""s hull one may take the hull for a beam and proceed with the argument of statics as follows. For a ship of overall length L and of total weight (including load) W, the variation of bending moment from bow to stern is graphically represented in FIG. 10(A) by the afore-mentioned simplification. The maximum bending moment, denoted by M, is proportional to the product of W and L, and it occurs at mid-ship location. This can be expressed by the following equation:
M=Wxc3x97L/C,
in which C is an empirical coefficient and, herein, is regarded to be a constant.
Now suppose the ship of overall length L and weight W is cut in half and becomes two ships of which each being of overall length {fraction (1/12)} L and weight {fraction (1/12)} W. Then, let Ms be the symbol of the maximum bending moment found in the small ship and, by the above equation, one arrives at
Ms=({fraction (1/12)}Wxc3x97xc2xdL)/C=xc2xc(Wxc3x97L)/C=xc2xcM;
i.e. it is only a quarter of the original maximum bending moment found in the ship of overall length L and weight W, as shown in FIG. 10(B). Albeit a simplification based on a simple theory, this realization, it is believed, serves well to indicate the merit of the present invention. Of course, the point is not to build two small ships, each sufficient unto itself, instead of a large one; for that would involve two sets of power generator, propeller, loading and unloading apparatus, and two groups of crew; moreover, that would be contrary to the aim of the inventor, which is to increase the dimensions of a ship, particularly applicable to an ocean-going merchantman with advantage, without rendering impossible to load and unload in a small harbor or to pass the Panama Canal.
In view of the foregoing discussion, the inventor herein discloses a novel ship design, thereby, it is hopeful, one can enlarge a ship""s hold for the sake of economy, without necessitating more power and material costs, nor incurring the danger of breaking up the ship at sea; and still, it will be shown, the embodiments of the invention can adjust themselves with ease to the more restrictive regulations of small harbor and, particularly, the Panama Canal.
Accordingly, to be more specific, the principal object of the invention is to provide a novel ship design of sectioned ship, wherein the ship is made up of at least two separate ship bodies, and one ship body is linked to the following one via a huge horizontally installed hinge means, thereby permitting of upward as well as downward angular motion of one ship body relative to another. The bending moment on such a sectioned ship is much smaller than that on a conventional ship of comparable dimensions; and, when the sectionized ship is in the act of plowing the waves, the flexible hinge means can absorb a portion of the force of incident waves, thus further reducing bending moment and the threat of hogging and sagging. Cost on fuel or power in sailing, as well as on material needed in ship-building, is also much reduced.
Another object of the invention is to provide a sectioned ship as disclosed in the foregoing, wherein said horizontal hinge means is so designed that it can be readily attached to, as well as detached from, one or both of the related ship bodies; so that, if need be, such as when approaching a small harbor or a certain quay, the sectioned ship can be taken apart by releasing the horizontal hinge means, and each division can be towed into the harbor or to the quay without much ado.
A further object of the invention is to provide a sectioned ship as disclosed in the foregoing, wherein said horizontal hinge means is an independent component of said sectioned ship, and it can be, within reasonable time, installed to connect one ship body with another.
Still another object of the invention is to provide a sectioned ship as disclosed in the foregoing, wherein said horizontal hinge means is covered up by steel plates from ship""s bottom as well as at the sides, so as to shield off water, and so as to reduce streamline disturbance due to the creation of hinge part amidships.
Still a further object of the invention is to provide a sectioned ship as disclosed in the foregoing, wherein a vertical pivoting part, like the combination of two up- side-down L-shaped cranks, is mounted on said sectionized ship, close to either side of the ship, and crossing over a separable interface of one ship body and the related horizontal hinge means, so that, as soon as the horizontal hinge means is disengaged at said interface, the sectioned ship can be horizontally folded round the vertical pivoting part by as wide as 180xc2x0, and the ship is thus shortened in its overall length. Such measure may be also of value for the sectioned ship to turn about in a small harbor or, for example, in entering the locks of the Panama Canal.
Other objects and features of the invention, will be better understood from the following description of embodiments thereof and the accompanying drawings.